(OKLAHOMA CITY) — Scientists at the Oklahoma Medical Research Foundation (OMRF) have announced the discovery of a new interferon-like substance they named “limitin” because of its ability to limit tumor cell growth. Limitin is partially similar in structure to the type I interferons, naturally occurring proteins first discovered for their ability to curtail viral replication. However, limitin was discovered in an unexpected way and may have unique biological activities. Limitin arrests the division of some mouse cell tumors in culture and causes other tumors to die. This discovery and an initial description of limitin activities will be described in the June issue of Nature Medicine.
Limitin was first isolated from cells of bone marrow responsible for regulating blood cell development. Instead of promoting blood cell growth, limitin was actively suppressive. This phase of the work was completed by Kay Medina, Ph.D. and Paul W. Kincade, Ph.D., both researchers at OMRF. Kenji Oritani, M.D., Ph.D., now an Assistant Professor at Osaka University, began a search for the gene encoding limitin during Postdoctoral studies in Oklahoma. One third of the limitin sequence resembles interferons, and limitin works through an interferon receptor on cells. The human counterpart of limitin is now being sought with the hope that it will be beneficial as a drug.
Interferons play important roles in the normal immune system. They are approved by the U.S. Food and Drug Administration for treatment of certain types of cancer, that include leukemia, melanoma, chronic myeloid leukemia and AIDS-related sarcoma. While the previously known interferons are also valuable as drugs for viral hepatitis and multiple sclerosis, there are many negative side effects.
For example, interferon treated patients may experience flu-like symptoms, fatigue, autoimmune reactions and depression. Limitin would be beneficial as a drug if it had fewer undesirable reactions than interferons. Several years will be required to learn the full range of responses by various normal cell types and tumors to limitin. This important information must be obtained before it could find applications as a drug.
Grants from the National Institutes of Health have supported Dr. Kincade’s studies of bone marrow since 1974. Dr. Oritani and his colleague Dr. Yoshiaki Yomiyama are members of a Japanese team led by Professor Yuji Matsuzawa at Osaka University.